This application claims benefit of Japanese Application No. 2000-229509 filed in Japan on Jul. 28, 2000, the contents of which are incorporated by this reference.
1. Field of the Invention
The present invention relates to an endoscope having a soft insertion member and capable of being sterilized with high-temperature high-pressure steam.
2. Description of the Related Art
In recent years, endoscopes have been widely employed in the field of medicine and the field of industry alike. The related arts of the endoscopes include an art disclosed in Japanese Unexamined Utility Model Publication No. 2-10802.
According to the Japanese Unexamined Utility Model Publication No. 2-10802, the flexibility of a flexible tube is changed at at least one point in an axial direction thereof so that it will be different between the back-and-forth portions of the flexible tube relative to the point. The flexibility in axial directions of at least one built-in component is changed in the middle of the built-in component. The point on the built-in component at which the flexibility of the built-in component is changed is located near the point on the flexible tube at which the flexibility of the flexible tube is changed.
In the foregoing structure, supposing the endoscope can be sterilized with high-temperature high-pressure steam, after sterilization is completed, the flexibilities of the flexible tube and built-in components vary. Consequently, the radii of curvature of the flexible tube and built-in components may change.
For example, the radius of curvature the built-in component exhibits after completion of sterilization with high-temperature high-pressure steam is larger than the radius of curvature the flexible tube exhibits after completion of the sterilization. In this case, when the flexible tube is bent, although the flexible tube is not buckled, the built-in component incorporated in the flexible tube may be buckled, which may cause certain inconvenience.
Accordingly, an object of the present invention is to provide an endoscope in which even after completion of sterilization with high-temperature high-pressure steam, unless a flexible tube buckles, a built-in component will not buckle.
Another object of the present invention is to provide a durable endoscope that is repeatedly usable for endoscopic examination.
An endoscope has a soft insertion member that includes a flexible tube. The flexible tube is flexible and has a flexible elongated built-in component incorporated therein. The endoscope withstands sterilization with high-temperature high-pressure steam during which an endoscope is sterilized while being exposed to high-temperature high-pressure steam.
A critical radius of curvature Rn exhibits the elongated built-in component after completion of sterilization with high-temperature high-pressure steam is equal to or smaller than a critical radius of curvature Rj the flexible tube exhibits after completion of the sterilization, that is, the condition of Rnxe2x89xa6Rj is met. Herein, after completion of sterilization with high-temperature high-pressure steam, if the elongated built-in component is bent to exhibit a radius of curvature equal to or smaller than the critical radius of curvature Rn, the elongated built-in component is buckled. After completion of the sterilization, if the flexible tube is bent to exhibit a radius of curvature equal to or smaller than the critical radius of curvature Rj, the flexible tube is buckled. Consequently, unless the flexible tube is bent to exhibit a radius of curvature equal to or smaller than the critical radius of curvature Rj that causes the flexible tube to buckle, the elongated built-in component will not buckle.